RESUMEN
Vernal pools are ephemeral wetlands that provide critical habitat to many listed species. Pesticide fate in vernal pools is poorly understood because of uncertainties in the amount of pesticide entering these ecosystems and their bioavailability throughout cycles of wet and dry periods. The Pesticide Water Calculator (PWC), a model used for the regulation of pesticides in the US, was used to predict surface water and sediment pore water pesticide concentrations in vernal pool habitats. The PWC model (version 1.59) was implemented with deterministic and probabilistic approaches and parameterized for three agricultural vernal pool watersheds located in the San Joaquin River basin in the Central Valley of California. Exposure concentrations for chlorpyrifos, diazinon and malathion were simulated. The deterministic approach used default values and professional judgment to calculate point values of estimated concentrations. In the probabilistic approach, Monte Carlo (MC) simulations were conducted across the full input parameter space with a sensitivity analysis that quantified the parameter contribution to model prediction uncertainty. Partial correlation coefficients were used as the primary sensitivity metric for analyzing model outputs. Conditioned daily sensitivity analysis indicates curve number (CN) and the universal soil loss equation (USLE) parameters as the most important environmental parameters. Therefore, exposure estimation can be improved efficiently by focusing parameterization efforts on these driving processes, and agricultural pesticide inputs in these critical habitats can be reduced by best management practices focused on runoff and sediment reductions.
Asunto(s)
Plaguicidas/análisis , Contaminantes Químicos del Agua/análisis , Agricultura , California , Cloropirifos/análisis , Ecosistema , Monitoreo del Ambiente , Suelo , Movimientos del Agua , HumedalesRESUMEN
We compared 2 statistical hypothesis-test approaches (no-observed-effect concentration [NOEC] and test of significant toxicity [TST]) to determine the influence of laboratory test performance on the false-positive error rate using the US Environmental Protection Agency's Ceriodaphnia dubia reproduction whole-effluent toxicity (WET) test endpoint. Simulation and power calculations were used to determine error rates based on observed control coefficients of variation (CV) for 8 laboratories over a range of effect levels. Average C. dubia control reproduction among laboratories was 20 to 40 offspring per female, and the 75th percentile CV was 0.10 to 0.31, reflecting a range in laboratory performance. The 2 approaches behave similarly for CVs of 0.2 to 0.3. At effects <10%, as CV decreases, TST is less likely to declare toxicity and NOEC is more likely to do so. Laboratory performance affects whether a sample is declared toxic and influences the probability of false-positive (and -negative) error rates using either approach. At the 75th percentile control CV observed for each laboratory, 4 laboratories would achieve approximately a 5% false-positive rate using 13 or fewer replicates for this test method. For the remaining 4 laboratories, more replicates would be needed to achieve a 5% false-positive rate. The present analyses demonstrate how false-positive rates are influenced by laboratory performance and WET test design. Environ Toxicol Chem 2019;38:511-523. Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.
Asunto(s)
Pruebas de Toxicidad/métodos , Animales , Cladóceros/efectos de los fármacos , Cladóceros/fisiología , Interpretación Estadística de Datos , Femenino , Reproducción/efectos de los fármacos , Estados Unidos , United States Environmental Protection Agency , Contaminantes Químicos del Agua/toxicidadRESUMEN
There is a great diversity of sources of chemical contaminants and stressors over large geographic areas. Chemical contaminant inputs and magnitude can potentially exhibit wide seasonal variation over large geographic areas. Together, these factors make linking exposure to monitored chemical contaminants and effects difficult. In practice, this linkage typically relies on relatively limited chemical occurrence data loosely coupled with individual effects, and population- or community-level assessments. Increased discriminatory power may be gained by approaching watershed level assessment in a more holistic manner, drawing from a number of disciplines that target endpoints spanning levels of the biological hierarchy. Using the Sacramento River as a case study, the present study aimed to 1) evaluate the performance of new analytical and biomarker tools in a real world setting and their potential for linking occurrence and effect; 2) characterize the effects of geographic and temporal variability through the integration of suborganismal, tissue, and individual level endpoints, as well as extensive chemical analyses; 3) identify knowledge gaps and research needs that limit the implementation of this holistic approach; and 4) provide an experimental design workflow for these types of assessments. Sites were selected to target inputs into the Sacramento River as it transitions from an agricultural to a mixed but primarily urban landscape. Chemical analyses were conducted on surface water samples at each site in both the spring and fall for pesticides, hormones, and active pharmaceutical ingredients (APIs). Active pharmaceutical ingredients were more often detected across sampling events in the fall; however, at the most downstream site the number of analytes detected and their concentrations were greater in the spring, which may be due to seasonal differences in rainfall. Changes in gene and protein expression targeting endocrine and reproductive effects were observed within each sampling event; however, they were inconsistent across seasons. Larval mortality at the most downstream site was seen in both seasons; however, behavioral changes were only observed in the spring. No clear linkages of specific analyte exposure to biological response were observed, nor were linkages across biological levels of organization. This failure may have resulted from limitations of the scope of molecular endpoints used, inconsistent timing of exposure, or discordance of analytical chemistry through grab sampling and longer term, integrative exposure. Together, results indicate a complicated view of the watershed.
Asunto(s)
Monitoreo del Ambiente/métodos , Contaminantes Químicos del Agua/análisis , Contaminación Química del Agua/estadística & datos numéricos , Conducta Cooperativa , San FranciscoRESUMEN
The test of significant toxicity (TST) is a hypothesis-testing approach based on bioequivalence developed by the U.S. Environmental Protection Agency (U.S. EPA) for analyzing whole-effluent toxicity (WET) and ambient toxicity data. The present study compares results of acute and chronic toxicity tests of effluent, storm-water, and ambient (i.e., receiving-water) samples using both the TST and the standard no-observed-effect concentration (NOEC) approach. Valid WET data were analyzed from 890 tests provided by more than 25 dischargers in California and Washington, USA, representing the majority of test methods used in the U.S. WET program. An additional 3,201 freshwater chronic toxicity tests, obtained from ambient monitoring programs in California, were also analyzed. The TST and NOEC approaches both declared a low number (<6.5%) of tests toxic if effects were below the unacceptable toxicity regulatory management decision (RMD) of 25% effect in chronic tests or 20% effect in acute tests. However, those test methods having generally lower within-test variability and greater test power (e.g., urchin fertilization test) had a much lower percentage of tests declared toxic than the NOEC approach when effects were below the unacceptable toxicity RMD. In addition, the TST showed fewer tests to be nontoxic than NOEC if the test exhibited effects greater than the toxicity RMD (0.1 and 9.6% for TST and NOEC, respectively, for effluents and 0 and 9.5%, respectively, for ambient samples). Our results demonstrate that the TST is more likely to identify a toxic sample when effects are fairly substantial (≥ 25% effect in chronic testing and ≥ 20% effect in acute tests) and less likely to identify a sample as toxic when effects are negligible (≤ 10% effect). Furthermore, these results demonstrate that appropriate WET data interpretation benefits from having well-designed test methods with sufficient power to identify significant toxicity or biologically insignificant effects when they occur.
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Agua Dulce/química , Pruebas de Toxicidad/métodos , Contaminantes Químicos del Agua/toxicidad , California , Estados Unidos , United States Environmental Protection Agency , Washingtón , Eliminación de Residuos Líquidos , Contaminantes Químicos del Agua/análisis , Contaminación Química del Agua/estadística & datos numéricosRESUMEN
The U.S. Environmental Protection Agency (U.S. EPA) and state agencies evaluate the toxicity of effluent and surface water samples based on statistical endpoints derived from multiconcentration tests (e.g., no observed effect concentration, EC25). The test of significant toxicity (TST) analysis is a two-sample comparison test that uses Welch's t test to compare organism responses in a sample (effluent or surface water) with responses in a control or site sample. In general, any form of t test (Welch's t included) is appropriate only if the data meet assumptions of normality and homogeneous variances. Otherwise, nonparametric tests are recommended. TST was designed to use Welch's t as the statistical test for all whole effluent toxicity (WET) test data. The authors evaluated the suitability of using Welch's t test for analyzing two-sample toxicity (WET) data, and within the TST approach, by examining the distribution and variances of data from over 2,000 WET tests and by conducting multiple simulations of WET test data. Simulated data were generated having variances and nonnormal distributions similar to observed WET test data for control and the effluent treatment groups. The authors demonstrate that (1) moderately unequal variances (similar to WET data) have little effect on coverage of the t test or Welch t test (for normally distributed data), and (2) for nonnormally distributed data (similar in distribution to WET data) TST, using Welch's t test, has close to nominal coverage on the basis of simulations with up to a ninefold difference in variance between the effluent and control groups (â¼95th percentile based on observed WET test data).
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Monitoreo del Ambiente/métodos , Pruebas de Toxicidad/métodos , Contaminantes Químicos del Agua/toxicidad , Proyectos de Investigación , Estadística como Asunto , Pruebas de Toxicidad/normas , Estados Unidos , United States Environmental Protection Agency , Contaminantes Químicos del Agua/normasRESUMEN
The U.S. Environmental Protection Agency (U.S. EPA) and state agencies implement the Clean Water Act, in part, by evaluating the toxicity of effluent and surface water samples. A common goal for both regulatory authorities and permittees is confidence in an individual test result (e.g., no-observed-effect concentration [NOEC], pass/fail, 25% effective concentration [EC25]), which is used to make regulatory decisions, such as reasonable potential determinations, permit compliance, and watershed assessments. This paper discusses an additional statistical approach (test of significant toxicity [TST]), based on bioequivalence hypothesis testing, or, more appropriately, test of noninferiority, which examines whether there is a nontoxic effect at a single concentration of concern compared with a control. Unlike the traditional hypothesis testing approach in whole effluent toxicity (WET) testing, TST is designed to incorporate explicitly both α and ß error rates at levels of toxicity that are unacceptable and acceptable, given routine laboratory test performance for a given test method. Regulatory management decisions are used to identify unacceptable toxicity levels for acute and chronic tests, and the null hypothesis is constructed such that test power is associated with the ability to declare correctly a truly nontoxic sample as acceptable. This approach provides a positive incentive to generate high-quality WET data to make informed decisions regarding regulatory decisions. This paper illustrates how α and ß error rates were established for specific test method designs and tests the TST approach using both simulation analyses and actual WET data. In general, those WET test endpoints having higher routine (e.g., 50th percentile) within-test control variation, on average, have higher method-specific α values (type I error rate), to maintain a desired type II error rate. This paper delineates the technical underpinnings of this approach and demonstrates the benefits to both regulatory authorities and permitted entities.
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Pruebas de Toxicidad/métodos , Contaminantes Químicos del Agua/toxicidad , Contaminación Química del Agua/estadística & datos numéricos , Interpretación Estadística de Datos , Pruebas de Toxicidad/normas , Pruebas de Toxicidad/estadística & datos numéricos , Estados Unidos , United States Environmental Protection Agency , Contaminantes Químicos del Agua/análisisRESUMEN
Irrigation and storm water runoff from agricultural fields has the potential to cause impairment to downstream aquatic receiving systems. Over the last several years, scientists have discovered the benefit of using edge-of-field practices, such as vegetated agricultural drainage ditches, in the mitigation of pesticides and sediment. After demonstrating this practice's feasibility in California, field trials were initiated to document irrigation runoff pesticide mitigation in California alfalfa and tomato fields. In the alfalfa field, chlorpyrifos concentration was decreased by 20% from the inflow to the ditch outflow. Thirty-two percent of the measured chlorpyrifos mass was associated with ditch plant material. In the tomato field, permethrin concentration was decreased by 67% and there was a 35% reduction in suspended sediment concentration from inflow to the ditch outflow. When surface water was not present in the ditch systems, the sediment was a significant repository for pesticides. Based on the field trials, vegetated agricultural drainage ditches can be successfully used as part of a suite of management practices to reduce pesticide and sediment runoff into aquatic receiving systems.
Asunto(s)
Agricultura/métodos , Drenaje de Agua/métodos , Plaguicidas/análisis , Plantas/metabolismo , Contaminantes Químicos del Agua/análisis , Contaminación Química del Agua/prevención & control , Biodegradación Ambiental , California , Cloropirifos/análisis , Cloropirifos/metabolismo , Solanum lycopersicum , Medicago sativa , Permetrina/análisis , Permetrina/metabolismo , Plaguicidas/metabolismo , Desarrollo de la Planta , Contaminantes Químicos del Agua/metabolismo , Contaminación Química del Agua/estadística & datos numéricosRESUMEN
The current study investigated the potential of vegetated drainage ditches for mitigating the impact of agricultural irrigation runoff on downstream aquatic ecosystems. Water column toxicity to larval fathead minnow (Pimephales promelas),and the amphipod Hyalella azteca was measured for 12 h or less at the ditch inflow and outflow, using custom-built in situ exposure systems. In addition, water and sediment samples were subject to standard toxicity tests with Ceriodaphnia dubia and H. azteca, respectively. No acute toxicity to larval fathead minnow was observed; however, runoff was highly toxic to invertebrates. Passage through a 389- to 402-m section of vegetated ditch had a mitigating effect and reduced toxicity to some degree. However, runoff from an alfalfa field treated with chlorpyrifos remained highly toxic to both invertebrate species, and runoff from a tomato field treated with permethrin remained highly toxic to H. azteca after passage through the ditch. Predicted toxic units calculated from insecticide concentrations in runoff and 96-h median lethal concentration (LC50) values generally agreed with C. dubia toxicity measured in the laboratory but significantly underestimated in situ toxicity to H. azteca. Sediments collected near the ditch outflow were toxic to H. azteca. Results from the current study demonstrate that experimental vegetated ditches were unable to eliminate the risk of irrigation runoff to aquatic ecosystems. In addition, protective measures based on chemical concentrations or laboratory toxicity tests with C. dubia do not ensure adequate protection of aquatic ecosystems from pyrethroid-associated toxicity.
Asunto(s)
Riego Agrícola/métodos , Contaminación Ambiental/prevención & control , Contaminación del Agua/prevención & control , California , Solanum lycopersicum , Medicago sativa , Estados Unidos , Contaminantes Químicos del Agua/químicaRESUMEN
Aquatic toxicity tests are laboratory experiments that measure the biological effect (e.g., growth, survival, reproduction) of effluents, receiving waters, or storm water on aquatic organisms. These toxicity tests must be performed using the best laboratory practices, and every effort must be made to enhance repeatability of the test method. We evaluated the generated reference toxicant test data for insurance of a level of quality assurance for tests over time within a laboratory and among laboratories. We recommend the reporting and evaluation of the percent minimum significant difference (PMSD) value for all toxicity test results. The minimum significant difference (MSD) represents the smallest difference between the control mean and a treatment mean that leads to the statistical rejection of the null hypothesis (i.e., no toxicity) at each concentration of the toxicity test dilution series. The MSD provides an indication of within-test variability, and smaller values of MSD are associated with increased power to detect a toxic effect. We recommend upper and lower PMSD bounds for each test method in order to minimize within-test variability and increase statistical power. To ensure that PMSD does not exceed an upper bound, testing laboratories may need to increase replication, decrease variability among replicates, or increase the control mean performance.
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Contaminantes Ambientales/toxicidad , Pruebas de Toxicidad/estadística & datos numéricos , Pruebas de Toxicidad/normas , Animales , Interpretación Estadística de Datos , Valores de Referencia , Reproducibilidad de los Resultados , Proyectos de Investigación , Estados Unidos , United States Environmental Protection AgencyRESUMEN
California (USA) agriculture employs pyrethroid and organophosphate insecticides to control insects in orchards and other crops. Diazinon and esfenvalerate were selected for this study because of their application overlaps. Toxicological and biochemical responses of larval fathead minnows (Pimephales promelas) exposed singly and in combinations to esfenvalerate and diazinon were determined. Exposures were 96-h static renewal tests that used standard U.S. Environmental Protection Agency acute toxicity test methods. After pesticide exposures, larvae were evaluated for carboxylesterase and acetylcholinesterase activity, and histopathological effects. Carboxylesterase activity was examined because of its potential influence on the toxicity of both organophosphates and pyrethroids. In vivo studies demonstrated that diazinon significantly inhibited carboxylesterase activity at nominal water concentrations as low as 50 microg/L. However, esfenvalerate did not affect carboxylesterase activity at any concentration tested. Liver glycogen depletion was the only histopathological effect observed; this effect was demonstrated with the individual pesticides and pesticide combinations (i.e., mixtures). The combinations of diazinon and esfenvalerate causing acute toxicity to fathead minnow larvae appeared to be greater than additive (i.e., synergistic) in all three tests.